1. Field of the Invention
The invention is based on a magnetic tape apparatus according to the precharacterizing clause of claim 1.
2. Discussion of the Background
It is known to record large quantities of digital data onto a magnetic tape at an extraordinarily high bit rate, i.e. in an extremely short time, by a matrix head see EP 89401125.3. Thanks to the matrix head, which makes possible the recording of a multiplicity of parallel tracks without guard bands, the same recording density can be achieved with a fixed head as in helical scan recording.
Since the relative speed between tape and head in longitudinal track recording with a multiplicity of parallel tracks is low, the scanning during playback has to take place with transducers which supply a speed-independent signal voltage. These are, for example, magnetoresistive heads, or heads which utilize the magnetooptical Kerr effect. A scanning device for a multiplicity of parallel tracks in which a laser beam is modulated by the magnetization of the adjacent tracks and is projected onto a CCD array, to be precise in such a way that each pixel of the CCD array receives the light modulated by the changes in magnetization of an individual track, is described in EP 89401125.3.
The number of pixels of the CCD array may also be greater than the number of simultaneously scanned tracks, so that an overscanning of the adjacent tracks takes place with the CCD array. By digital filtering, the signals of the individual tracks can then be separated, without exact tracking control being required. The coarse setting to a specific track region is made possible by the CCD array being designed such that it covers an enlarged track region, and the selection of the desired track region takes place using electronic means.
As a result, the accuracy requirements for the head displacement mechanism, required for the selection of different track regions, can be reduced significantly.
The signal voltage derived from the clock voltages of the CCD array represents the binary values of the adjacent bit cells in the parallel tracks. By suitable synchronizing information, the originally recorded signal can be restored using digital signal processing means.